A lubricating agent is used in order to easily mount tire beads on a wheel when assembling a tire and a wheel. Assembly involves mounting and releasing (see, PTL 1 and 2). Conventionally used lubricating agents include solid types and water-soluble types. Solid types are often used for mounting, while water-soluble types are used only for releasing. Solid types do not penetrate readily between the wheel and the beads, and are not suitable for releasing.
Although sufficient lubricating performance is exhibited when water-soluble types for tire release are used, some residual lubricating agent remains on the tire and on the wheel after release from the wheel. The residual lubricating agent must be removed cleanly before the tire and wheel are used again.
To mount of the tire onto the wheel, bead seating pressure is applied with a view to promoting spontaneous mounting of the tire beads onto the wheel. In notifications pertaining to Occupational Health and Safety Regulations, the prescribed upper limit of the bead seating pressure is 300 kPa, with a view to securing operator safety.
For larger tire sizes, however, mounting of the tire onto the wheel at a bead seating pressure of 300 kPa is not easy even when using a lubricating agent of solid type, and in some instances mounting can be completed only by applying a bead seating pressure that exceeds 300 kPa. Also, the tire may in some cases be mounted to the wheel using lubricating agents having the property of being residually present after mounting, and which are generally not approved for use as a lubricating agent for tire beads. The former instance is undesirable in terms of securing operator safety, while the latter is undesirable from the viewpoint of safe driving of an automobile.